<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录页面</title>
    <style>
        * {
            margin: 0;
        }

        #app {
            width: 300px;
            border: 2px solid red;
            margin: auto;
        }

        h2 {
            font-size: 16px;
            padding: 16px 0;
            color: white;
            background: pink;
        }

        form {
            background-color: rgb(50, 175, 168);
        }

        div:nth-child(1) > input {
            border: 3px solid black;
        }

        div:nth-child(2) > input {
            border: 3px dashed deeppink;
        }

        div:nth-child(3) > input {
            border: 3px dashed orangered;
        }
    </style>
</head>
<body>

<div id="app">
    <h2>会员登录</h2>
    <form action="#">
        <div>
            <span>用户名: </span><input type="text" name="username"/>
        </div>
        <div>
            <span>密码: </span><input type="password" name="password"/>
        </div>
        <div>
            <span>邮箱: </span><input type="email" name="email"/>
        </div>
    </form>
</div>

</body>
</html>